Re: [Elecraft] Question about antenna matching

[David Gilbert]

Actually, I never suggested a Q for the coil.  Al must have been 
thinking about somebody else when he said that part, although the rest 
of what he attributed to me is accurate.  I usually use a Q of 200  for 
an air core coil if I'm trying to be conservative, but a Q of 400 is 
reasonable if you have room for a coil of decent size and as you say, 
700-800 is achievable if you have the ability to optimize it.   I have 
no idea what the Q of a ferrite core inductor in a typical antenna tuner is.


Your description of the MN-2700 makes me want to go look for one. ;)

73,
Dave   AB7E



On 7/14/2021 3:49 AM, Alan Bloom wrote:
The Drake tuners used a Pi-L circuit topology in which the circulating 
current in the inductor is independent of the load impedance. Assuming 
almost all the loss is in the inductor, that means that the loss is 
independent of the load impedance.


(Another advantage of that topology is you get good harmonic 
suppression for all load impedances.)


So when I was designing the Drake MN-2700 I just measured the loss 
into a 50 ohm load and made sure it was less than the 0.5 dB spec with 
some margin.  That won't work when using most topologies (such as the 
L networks used in the Elecraft tuners) because the loss does change 
drastically depending on the load impedance.  For those, you can use 
two identical tuners back to back, both adjusted for the same load 
impedance.  The loss for each tuner is approximately half the measured 
loss.  (I think I did do a few tests like that on the MN-2700 just as 
a sanity check.)


I found that the hardest band to get to meet all specs (5:1 SWR, 0.5 
dB loss, 1000W average, 2000W PEP) was 160 meters.  That's partly 
because it is hard to get a high-inductance, super high-Q coil small 
enough to fit in the cabinet and partly because of the large 
capacitances required.  (The MN-2700 has 3-position switches to add 
fixed capacitance to each tuning capacitor.)


To measure the matching capability at different phase angles, I just 
connected a 50-ohm load to the input and an HP impedance analyzer to 
the output.  By adjusting each tuning capacitor throughout its range 
and plotting the results on a Smith chart you can see the (complex 
conjugate of the) matching range.  Actually the output impedance of 
the tuner and the antenna impedance it matches are not exactly 
conjugates, but are close as long as the tuner insertion loss is low.


As suggested by Dave, I chose typical Q values of 100 for the inductor


The coils in the MN-2700 have much higher Q than that.  To such an 
extent that it was difficult to get accurate readings on an HP 
Q-meter.  But by tightening the connecting bolts down as hard as 
possible and making sure there were no absorbing objects (like human 
hands) in the near field of the inductor I was getting values in the 
700-800 range on some bands as I recall.  (These were all air-wound 
solenoidal inductors.)


Alan N1AL


On 7/13/2021 10:32 AM, Al Lorona wrote:
Thanks to Al N1AL, Jack W6FB, and Dave AB7E for great information 
that helped me a lot.


I'm in the circuit simulation business, after all, and I confess that 
I was just being lazy, so I ran some simulations that confirmed what 
Dave, in particular, had said.


As suggested by Dave, I chose typical Q values of 100 for the 
inductor and 1000 for the capacitor. Then I simulated as many points 
as I could on the entire Smith Chart to see 1/ if the tuner could 
tune each point to 50 ohms, and 2/ what the power loss was in the 
tuner at each of those points. Then, I discovered that K6JCA had 
already done this on his excellent blog 
at:  https://k6jca.blogspot.com/2015/03/notes-on-antenna-tuners-l-network-and.html . The 
guy is totally professional and exhaustive in his discussions. I 
really admire his work.


Anyway, it turns out you can make a graph of power lost in the tuner 
versus phase angle of the load. As you might suspect, 'easy' loads of 
5 or 500 ohms resistive (SWR = 10:1) don't tax a tuner as much as 
reactive loads do. In fact, they're near (but interestingly, not at) 
the areas of *minimum* power loss.


Whenever an antenna tuner is reviewed in QST, resistive mismatched 
loads are usually used. I'd like to see tuners tested with reactive 
loads, but the number of loads required to do this from 160 to 10 
meters would be enormous. I see why resistive loads are preferred, 
because you can re-use the loads on every band.


I'm frustrated by imprecise statements like, "This tuner will tune an 
8:1 mismatch." What does that mean? There has to be a better way for 
manufacturers to spec the exact impedance ranges that their tuners 
will tune. I like the method that I used, which shades a Smith Chart 
in color based on the two criteria I listed above. One picture would 
tell you all about a tuner's effectiveness. No real tuner can tune 
the entire Smith Chart, but the more of the chart that is covered, 
the better the tuner. And if you can shade the areas of higher 

Re: [Elecraft] Question about antenna matching

[Alan Bloom]

The Drake tuners used a Pi-L circuit topology in which the circulating 
current in the inductor is independent of the load impedance.  Assuming 
almost all the loss is in the inductor, that means that the loss is 
independent of the load impedance.


(Another advantage of that topology is you get good harmonic suppression 
for all load impedances.)


So when I was designing the Drake MN-2700 I just measured the loss into 
a 50 ohm load and made sure it was less than the 0.5 dB spec with some 
margin.  That won't work when using most topologies (such as the L 
networks used in the Elecraft tuners) because the loss does change 
drastically depending on the load impedance.  For those, you can use two 
identical tuners back to back, both adjusted for the same load 
impedance.  The loss for each tuner is approximately half the measured 
loss.  (I think I did do a few tests like that on the MN-2700 just as a 
sanity check.)


I found that the hardest band to get to meet all specs (5:1 SWR, 0.5 dB 
loss, 1000W average, 2000W PEP) was 160 meters.  That's partly because 
it is hard to get a high-inductance, super high-Q coil small enough to 
fit in the cabinet and partly because of the large capacitances 
required.  (The MN-2700 has 3-position switches to add fixed capacitance 
to each tuning capacitor.)


To measure the matching capability at different phase angles, I just 
connected a 50-ohm load to the input and an HP impedance analyzer to the 
output.  By adjusting each tuning capacitor throughout its range and 
plotting the results on a Smith chart you can see the (complex conjugate 
of the) matching range.  Actually the output impedance of the tuner and 
the antenna impedance it matches are not exactly conjugates, but are 
close as long as the tuner insertion loss is low.


As suggested by Dave, I chose typical Q values of 100 for the inductor


The coils in the MN-2700 have much higher Q than that.  To such an 
extent that it was difficult to get accurate readings on an HP Q-meter.  
But by tightening the connecting bolts down as hard as possible and 
making sure there were no absorbing objects (like human hands) in the 
near field of the inductor I was getting values in the 700-800 range on 
some bands as I recall.  (These were all air-wound solenoidal inductors.)


Alan N1AL


On 7/13/2021 10:32 AM, Al Lorona wrote:

Thanks to Al N1AL, Jack W6FB, and Dave AB7E for great information that helped 
me a lot.

I'm in the circuit simulation business, after all, and I confess that I was 
just being lazy, so I ran some simulations that confirmed what Dave, in 
particular, had said.

As suggested by Dave, I chose typical Q values of 100 for the inductor and 1000 
for the capacitor. Then I simulated as many points as I could on the entire 
Smith Chart to see 1/ if the tuner could tune each point to 50 ohms, and 2/ 
what the power loss was in the tuner at each of those points. Then, I 
discovered that K6JCA had already done this on his excellent blog at:  
https://k6jca.blogspot.com/2015/03/notes-on-antenna-tuners-l-network-and.html . 
The guy is totally professional and exhaustive in his discussions. I really 
admire his work.

Anyway, it turns out you can make a graph of power lost in the tuner versus 
phase angle of the load. As you might suspect, 'easy' loads of 5 or 500 ohms 
resistive (SWR = 10:1) don't tax a tuner as much as reactive loads do. In fact, 
they're near (but interestingly, not at) the areas of *minimum* power loss.

Whenever an antenna tuner is reviewed in QST, resistive mismatched loads are 
usually used. I'd like to see tuners tested with reactive loads, but the number 
of loads required to do this from 160 to 10 meters would be enormous. I see why 
resistive loads are preferred, because you can re-use the loads on every band.

I'm frustrated by imprecise statements like, "This tuner will tune an 8:1 
mismatch." What does that mean? There has to be a better way for manufacturers to 
spec the exact impedance ranges that their tuners will tune. I like the method that I 
used, which shades a Smith Chart in color based on the two criteria I listed above. One 
picture would tell you all about a tuner's effectiveness. No real tuner can tune the 
entire Smith Chart, but the more of the chart that is covered, the better the tuner. And 
if you can shade the areas of higher tuner loss in red, then that would also tell you an 
important piece of information. (However, to generate such a plot through measurement 
you'd probably need a very expensive load-pull setup, which is a totally separate 
discussion.)

For the L-network I simulated, a particularly difficult 10:1 load was near the 7 - 
 j30 ohm point, which is toward the bottom edge of the Smith Chart at a phase 
angle of 282 degrees (or -77 degrees), and a similar point near the top edge. The 
lower impedances with capacitive reactance were definitely the most difficult 
(using power loss as the measure of 'difficulty') for the tuner to handle, which 

Re: [Elecraft] Question about antenna matching

[CUTTER DAVID via Elecraft]

You might find some answers here:
https://www.dj0ip.de/antenna-matchboxes/
On the next page he shows all the results from published data. 

David G3UNA

> On 14 July 2021 at 07:29 Julia Tuttle  wrote:
> 
> 
> That doesn't actually answer the question "what are manufacturers measuring
> when they quote 10:1 matching ability?", and makes a gross and insulting
> generalization about the quality of equipment produced for the amateur
> radio market.
> 
> On Wed, Jul 14, 2021, 01:45 Ray  wrote:
> 
> > The Statement  "This tuner will tune an 8:1 mismatch."
> > Is made in an Armature world, buy an Amateur person,
> > Not for a Professional Product by  Calibrated Test Equipment.
> > This is Not New, it has happened for Decades.  Buyer Beware.
> > WA6VAB  Ray  K3
> >
> >
> > From: Al Lorona
> > Sent: Tuesday, July 13, 2021 9:32 AM
> > To: elecraft@mailman.qth.net
> > Subject: Re: [Elecraft] Question about antenna matching
> >
> > Thanks to Al N1AL, Jack W6FB, and Dave AB7E for great information that
> > helped me a lot.
> >
> > I'm in the circuit simulation business, after all, and I confess that I
> > was just being lazy, so I ran some simulations that confirmed what Dave, in
> > particular, had said.
> >
> > As suggested by Dave, I chose typical Q values of 100 for the inductor and
> > 1000 for the capacitor. Then I simulated as many points as I could on the
> > entire Smith Chart to see 1/ if the tuner could tune each point to 50 ohms,
> > and 2/ what the power loss was in the tuner at each of those points. Then,
> > I discovered that K6JCA had already done this on his excellent blog at:
> > https://k6jca.blogspot.com/2015/03/notes-on-antenna-tuners-l-network-and.html
> >  . The
> > guy is totally professional and exhaustive in his discussions. I really
> > admire his work.
> >
> > Anyway, it turns out you can make a graph of power lost in the tuner
> > versus phase angle of the load. As you might suspect, 'easy' loads of 5 or
> > 500 ohms resistive (SWR = 10:1) don't tax a tuner as much as reactive loads
> > do. In fact, they're near (but interestingly, not at) the areas of
> > *minimum* power loss.
> >
> > Whenever an antenna tuner is reviewed in QST, resistive mismatched loads
> > are usually used. I'd like to see tuners tested with reactive loads, but
> > the number of loads required to do this from 160 to 10 meters would be
> > enormous. I see why resistive loads are preferred, because you can re-use
> > the loads on every band.
> >
> > I'm frustrated by imprecise statements like, "This tuner will tune an 8:1
> > mismatch." What does that mean? There has to be a better way for
> > manufacturers to spec the exact impedance ranges that their tuners will
> > tune. I like the method that I used, which shades a Smith Chart in color
> > based on the two criteria I listed above. One picture would tell you all
> > about a tuner's effectiveness. No real tuner can tune the entire Smith
> > Chart, but the more of the chart that is covered, the better the tuner. And
> > if you can shade the areas of higher tuner loss in red, then that would
> > also tell you an important piece of information. (However, to generate such
> > a plot through measurement you'd probably need a very expensive load-pull
> > setup, which is a totally separate discussion.)
> >
> > For the L-network I simulated, a particularly difficult 10:1 load was near
> > the 7 -  j30 ohm point, which is toward the bottom edge of the Smith Chart
> > at a phase angle of 282 degrees (or -77 degrees), and a similar point near
> > the top edge. The lower impedances with capacitive reactance were
> > definitely the most difficult (using power loss as the measure of
> > 'difficulty') for the tuner to handle, which Dave stated in his post, while
> > the high impedances with inductive reactance were generally more difficult.
> > If your antenna must be mismatched, and you're using an L-network tuner,
> > you want it to be > 50 ohms with a little bit of capacitive reactance, or
> > below 50 and inductive.
> >
> > By the way, K6JCA actually put the Elecraft KAT500 through this simulated
> > evaluation and it tested so well that he ended up buying one.
> >
> >
> > Al  W6LX/4
> >
> >
> > __
> > Elecraft mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/elecraft
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:Elecraft@mailman.qth.net
> >
> > This list h

Re: [Elecraft] Question about antenna matching

[Julia Tuttle]

That doesn't actually answer the question "what are manufacturers measuring
when they quote 10:1 matching ability?", and makes a gross and insulting
generalization about the quality of equipment produced for the amateur
radio market.

On Wed, Jul 14, 2021, 01:45 Ray  wrote:

> The Statement  "This tuner will tune an 8:1 mismatch."
> Is made in an Armature world, buy an Amateur person,
> Not for a Professional Product by  Calibrated Test Equipment.
> This is Not New, it has happened for Decades.  Buyer Beware.
> WA6VAB  Ray  K3
>
>
> From: Al Lorona
> Sent: Tuesday, July 13, 2021 9:32 AM
> To: elecraft@mailman.qth.net
> Subject: Re: [Elecraft] Question about antenna matching
>
> Thanks to Al N1AL, Jack W6FB, and Dave AB7E for great information that
> helped me a lot.
>
> I'm in the circuit simulation business, after all, and I confess that I
> was just being lazy, so I ran some simulations that confirmed what Dave, in
> particular, had said.
>
> As suggested by Dave, I chose typical Q values of 100 for the inductor and
> 1000 for the capacitor. Then I simulated as many points as I could on the
> entire Smith Chart to see 1/ if the tuner could tune each point to 50 ohms,
> and 2/ what the power loss was in the tuner at each of those points. Then,
> I discovered that K6JCA had already done this on his excellent blog at:
> https://k6jca.blogspot.com/2015/03/notes-on-antenna-tuners-l-network-and.html 
> . The
> guy is totally professional and exhaustive in his discussions. I really
> admire his work.
>
> Anyway, it turns out you can make a graph of power lost in the tuner
> versus phase angle of the load. As you might suspect, 'easy' loads of 5 or
> 500 ohms resistive (SWR = 10:1) don't tax a tuner as much as reactive loads
> do. In fact, they're near (but interestingly, not at) the areas of
> *minimum* power loss.
>
> Whenever an antenna tuner is reviewed in QST, resistive mismatched loads
> are usually used. I'd like to see tuners tested with reactive loads, but
> the number of loads required to do this from 160 to 10 meters would be
> enormous. I see why resistive loads are preferred, because you can re-use
> the loads on every band.
>
> I'm frustrated by imprecise statements like, "This tuner will tune an 8:1
> mismatch." What does that mean? There has to be a better way for
> manufacturers to spec the exact impedance ranges that their tuners will
> tune. I like the method that I used, which shades a Smith Chart in color
> based on the two criteria I listed above. One picture would tell you all
> about a tuner's effectiveness. No real tuner can tune the entire Smith
> Chart, but the more of the chart that is covered, the better the tuner. And
> if you can shade the areas of higher tuner loss in red, then that would
> also tell you an important piece of information. (However, to generate such
> a plot through measurement you'd probably need a very expensive load-pull
> setup, which is a totally separate discussion.)
>
> For the L-network I simulated, a particularly difficult 10:1 load was near
> the 7 -  j30 ohm point, which is toward the bottom edge of the Smith Chart
> at a phase angle of 282 degrees (or -77 degrees), and a similar point near
> the top edge. The lower impedances with capacitive reactance were
> definitely the most difficult (using power loss as the measure of
> 'difficulty') for the tuner to handle, which Dave stated in his post, while
> the high impedances with inductive reactance were generally more difficult.
> If your antenna must be mismatched, and you're using an L-network tuner,
> you want it to be > 50 ohms with a little bit of capacitive reactance, or
> below 50 and inductive.
>
> By the way, K6JCA actually put the Elecraft KAT500 through this simulated
> evaluation and it tested so well that he ended up buying one.
>
>
> Al  W6LX/4
>
>
> __
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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> Post: mailto:Elecraft@mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
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>
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Re: [Elecraft] Question about antenna matching

[Ray]

The Statement  "This tuner will tune an 8:1 mismatch."
Is made in an Armature world, buy an Amateur person,
Not for a Professional Product by  Calibrated Test Equipment.
This is Not New, it has happened for Decades.  Buyer Beware.
WA6VAB  Ray  K3   


From: Al Lorona
Sent: Tuesday, July 13, 2021 9:32 AM
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] Question about antenna matching

Thanks to Al N1AL, Jack W6FB, and Dave AB7E for great information that helped 
me a lot.

I'm in the circuit simulation business, after all, and I confess that I was 
just being lazy, so I ran some simulations that confirmed what Dave, in 
particular, had said.

As suggested by Dave, I chose typical Q values of 100 for the inductor and 1000 
for the capacitor. Then I simulated as many points as I could on the entire 
Smith Chart to see 1/ if the tuner could tune each point to 50 ohms, and 2/ 
what the power loss was in the tuner at each of those points. Then, I 
discovered that K6JCA had already done this on his excellent blog at:  
https://k6jca.blogspot.com/2015/03/notes-on-antenna-tuners-l-network-and.html . 
The guy is totally professional and exhaustive in his discussions. I really 
admire his work.

Anyway, it turns out you can make a graph of power lost in the tuner versus 
phase angle of the load. As you might suspect, 'easy' loads of 5 or 500 ohms 
resistive (SWR = 10:1) don't tax a tuner as much as reactive loads do. In fact, 
they're near (but interestingly, not at) the areas of *minimum* power loss.

Whenever an antenna tuner is reviewed in QST, resistive mismatched loads are 
usually used. I'd like to see tuners tested with reactive loads, but the number 
of loads required to do this from 160 to 10 meters would be enormous. I see why 
resistive loads are preferred, because you can re-use the loads on every band.

I'm frustrated by imprecise statements like, "This tuner will tune an 8:1 
mismatch." What does that mean? There has to be a better way for manufacturers 
to spec the exact impedance ranges that their tuners will tune. I like the 
method that I used, which shades a Smith Chart in color based on the two 
criteria I listed above. One picture would tell you all about a tuner's 
effectiveness. No real tuner can tune the entire Smith Chart, but the more of 
the chart that is covered, the better the tuner. And if you can shade the areas 
of higher tuner loss in red, then that would also tell you an important piece 
of information. (However, to generate such a plot through measurement you'd 
probably need a very expensive load-pull setup, which is a totally separate 
discussion.)

For the L-network I simulated, a particularly difficult 10:1 load was near the 
7 -  j30 ohm point, which is toward the bottom edge of the Smith Chart at a 
phase angle of 282 degrees (or -77 degrees), and a similar point near the top 
edge. The lower impedances with capacitive reactance were definitely the most 
difficult (using power loss as the measure of 'difficulty') for the tuner to 
handle, which Dave stated in his post, while the high impedances with inductive 
reactance were generally more difficult. If your antenna must be mismatched, 
and you're using an L-network tuner, you want it to be > 50 ohms with a little 
bit of capacitive reactance, or below 50 and inductive.

By the way, K6JCA actually put the Elecraft KAT500 through this simulated 
evaluation and it tested so well that he ended up buying one.


Al  W6LX/4


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Re: [Elecraft] Question about antenna matching

[Al Lorona]

Thanks to Al N1AL, Jack W6FB, and Dave AB7E for great information that helped 
me a lot.

I'm in the circuit simulation business, after all, and I confess that I was 
just being lazy, so I ran some simulations that confirmed what Dave, in 
particular, had said.

As suggested by Dave, I chose typical Q values of 100 for the inductor and 1000 
for the capacitor. Then I simulated as many points as I could on the entire 
Smith Chart to see 1/ if the tuner could tune each point to 50 ohms, and 2/ 
what the power loss was in the tuner at each of those points. Then, I 
discovered that K6JCA had already done this on his excellent blog at:  
https://k6jca.blogspot.com/2015/03/notes-on-antenna-tuners-l-network-and.html . 
The guy is totally professional and exhaustive in his discussions. I really 
admire his work.

Anyway, it turns out you can make a graph of power lost in the tuner versus 
phase angle of the load. As you might suspect, 'easy' loads of 5 or 500 ohms 
resistive (SWR = 10:1) don't tax a tuner as much as reactive loads do. In fact, 
they're near (but interestingly, not at) the areas of *minimum* power loss.

Whenever an antenna tuner is reviewed in QST, resistive mismatched loads are 
usually used. I'd like to see tuners tested with reactive loads, but the number 
of loads required to do this from 160 to 10 meters would be enormous. I see why 
resistive loads are preferred, because you can re-use the loads on every band.

I'm frustrated by imprecise statements like, "This tuner will tune an 8:1 
mismatch." What does that mean? There has to be a better way for manufacturers 
to spec the exact impedance ranges that their tuners will tune. I like the 
method that I used, which shades a Smith Chart in color based on the two 
criteria I listed above. One picture would tell you all about a tuner's 
effectiveness. No real tuner can tune the entire Smith Chart, but the more of 
the chart that is covered, the better the tuner. And if you can shade the areas 
of higher tuner loss in red, then that would also tell you an important piece 
of information. (However, to generate such a plot through measurement you'd 
probably need a very expensive load-pull setup, which is a totally separate 
discussion.)

For the L-network I simulated, a particularly difficult 10:1 load was near the 
7 -  j30 ohm point, which is toward the bottom edge of the Smith Chart at a 
phase angle of 282 degrees (or -77 degrees), and a similar point near the top 
edge. The lower impedances with capacitive reactance were definitely the most 
difficult (using power loss as the measure of 'difficulty') for the tuner to 
handle, which Dave stated in his post, while the high impedances with inductive 
reactance were generally more difficult. If your antenna must be mismatched, 
and you're using an L-network tuner, you want it to be > 50 ohms with a little 
bit of capacitive reactance, or below 50 and inductive.

By the way, K6JCA actually put the Elecraft KAT500 through this simulated 
evaluation and it tested so well that he ended up buying one.


Al  W6LX/4


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[Elecraft] Question about antenna matching

[Andy Durbin]

It's probably worth noting that KAT500 stores the bypass SWR (VSWRB) for every 
tuning solution (every bin and every antenna in that bin).  The bypass SWR is 
used to limit the power that can be applied to the tuner without it faulting.

e.g.

DM BN00;BIN 31;FR 1810-1819;ADDR 10612;
AN3;BYPN;SIDET;CE7;L19;VSWRB 2.40;
AN3;BYPN;SIDET;CA0;L10;VSWRB 1.93;
AN3;BYPN;SIDET;CFC;L1A;VSWRB 3.10;
AN3;BYPN;SIDET;CB4;L1A;VSWRB 2.66;
AN3;BYPB;VSWRB 1.00;
AN3;BYPN;SIDET;CC6;L18;VSWRB 2.37;

" Fault 2
Power Above Design Limit for Antenna SWR
Transmitter power exceeds the design limit for the unmatched antenna SWR. This 
power limit varies with the SWR of the antenna: 600 watts at 10:1 SWR, 1000 
watts at 3:1 SWR."

My notes say:

"The permitted power in watts is 7000 / bypass SWR, constrained between 250 and 
1800 watts."

The power limit implementation does not appear to depend on the L and C 
required to achieve a match but it could because those values are known.

73,
Andy, k3wyc
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[Elecraft] Question about antenna matching

[Bob McGraw]

Do note that the "Typical Matching Range and Power Limits" as stated on 
page 2 of the KAT500 manual.   Pay particular attention to the power 
handling and SWR range between 1.8 - 2.0 MHz.   The SWR limits are to 
5:1 Low impedance,  and 10:1 High impedance.


In the 3 - 30 MHz range the power can be 1000 max but with only a 3:1 
SWR or better.


Also note the Duty Cycle statement regarding power rating being ICAS, 
thus being equal time on and off with a 5 min. limit max at full power.


If you aren't sure, then err on the conservative side so one won't let 
the smoke out of the box.


73

Bob, K4TAX


Message: 2
Date: Sun, 11 Jul 2021 16:17:43 -0500
From: Jack Brindle
To: Elecraft Reflector
Subject: Re: [Elecraft] Question about antenna matching
Message-ID:<7cc60665-e824-4132-bc62-014d695d7...@me.com>
Content-Type: text/plain;   charset=utf-8

There is another big consideration in modern ATUs which use toroid cores for 
the inductors. The cores will heat up during transmission, especially for bad 
mismatches. Remember, the ATU still has to deal with the high reflected power 
as it provides a good match for the radio. If the heating reaches a critical 
level, the toroid will break, and the ATU will no longer be able to do its job. 
ATUs are thus rated for the amount of reflected power (thus SWR) they can 
handle with some margin for failure. An ATU like the KAT will handle higher 
mismatches at low power, but when you start trying to push lots of power 
through it, the heating margins drop, meaning that you should really watch the 
match when trying to run a kilowatt through an ATU in order to avoid damaging 
it. At 50 watts the KAT should handle a pretty bad mismatch, while at 500 a 
lower maximum mismatch should be observed.

Also note that at higher power the connectors, adapters and coax cable will 
also see lots of heating with big mismatches. These can fail also; in fact we 
see that a lot. That?s why you see lots of admonitions to only use high quality 
connectors and adapters. Right angle adapters are especially bad as the 
conductor tends to migrate and short out at high power. Be sure that you use 
coax that is rated for the power levels as well.

73,
Jack, W6FB

On 7/12/2021 10:24 AM, elecraft-requ...@mailman.qth.net wrote:

Message: 2
Date: Sun, 11 Jul 2021 16:17:43 -0500
From: Jack Brindle
To: Elecraft Reflector
Subject: Re: [Elecraft] Question about antenna matching
Message-ID:<7cc60665-e824-4132-bc62-014d695d7...@me.com>
Content-Type: text/plain;   charset=utf-8

There is another big consideration in modern ATUs which use toroid cores for 
the inductors. The cores will heat up during transmission, especially for bad 
mismatches. Remember, the ATU still has to deal with the high reflected power 
as it provides a good match for the radio. If the heating reaches a critical 
level, the toroid will break, and the ATU will no longer be able to do its job. 
ATUs are thus rated for the amount of reflected power (thus SWR) they can 
handle with some margin for failure. An ATU like the KAT will handle higher 
mismatches at low power, but when you start trying to push lots of power 
through it, the heating margins drop, meaning that you should really watch the 
match when trying to run a kilowatt through an ATU in order to avoid damaging 
it. At 50 watts the KAT should handle a pretty bad mismatch, while at 500 a 
lower maximum mismatch should be observed.

Also note that at higher power the connectors, adapters and coax cable will 
also see lots of heating with big mismatches. These can fail also; in fact we 
see that a lot. That?s why you see lots of admonitions to only use high quality 
connectors and adapters. Right angle adapters are especially bad as the 
conductor tends to migrate and short out at high power. Be sure that you use 
coax that is rated for the power levels as well.

73,
Jack, W6FB


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Re: [Elecraft] Question about antenna matching

[David Gilbert]

Hi, Al.

Yes, some mismatches are much more problematic than others, even for the 
same SWR.


One way to see this is to use TLW, the transmission line calculator that 
comes free with the ARRL Antenna Book.  Choose whatever load impedance 
you want in any combination of real and reactive values. Click the 
"Tuner" button to see various options for the tuner configuration and 
then set the Q for the capacitor(s) and coil to whatever you think is 
reasonable  The most common configurations would either be high pass 
L-Network or high pass T-network.


Not only will you see a diagram of the tuner with the required values to 
give a match, but you can see the voltage, current, and power loss 
(heating) for each component.  Try different load impedance combinations 
to see the different power losses.  The difference can be striking.


In general, low impedances will cause more tuner loss than higher 
impedances, and capacitive load reactance tends to be more problematic 
than inductive reactance.  That, of course, is mostly because real life 
inductors tend to have lower Q than capacitors, and that is certainly 
the case for auto tuners with ferrite core inductors.


As an aside, TLW is an amazing tool and most people don't give it the 
credit it is due.


73,
Dave   AB7E



On 7/11/2021 11:58 AM, Al Lorona wrote:

This question is about how manufacturers spec the matching range of their 
antenna tuners.

If an antenna system presents an impedance of 5 + j0 ohms to the antenna tuner, 
that's an SWR = 10 to 1.

But, an antenna impedance of 50 - j143 ohms is also SWR = 10. So is 110 - j200 
ohms.

When a manufacturer like Elecraft says, "Our antenna tuner can match a 10:1 
mismatch," does that mean the tuner can match the first case above, the second case, 
the third case, or all three?

I guess what I'm asking is, are all of the impedances above equally difficult 
for the same tuner to match? Or is one 'harder' than the others? It would 
depend on the values of the L and C in the tuner, wouldn't it? Which implies 
that certain 10:1 mismatches are not tunable?

Thanks,

Al  W6LX/4


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Re: [Elecraft] Question about antenna matching

[Jack Brindle via Elecraft]

There is another big consideration in modern ATUs which use toroid cores for 
the inductors. The cores will heat up during transmission, especially for bad 
mismatches. Remember, the ATU still has to deal with the high reflected power 
as it provides a good match for the radio. If the heating reaches a critical 
level, the toroid will break, and the ATU will no longer be able to do its job. 
ATUs are thus rated for the amount of reflected power (thus SWR) they can 
handle with some margin for failure. An ATU like the KAT will handle higher 
mismatches at low power, but when you start trying to push lots of power 
through it, the heating margins drop, meaning that you should really watch the 
match when trying to run a kilowatt through an ATU in order to avoid damaging 
it. At 50 watts the KAT should handle a pretty bad mismatch, while at 500 a 
lower maximum mismatch should be observed.

Also note that at higher power the connectors, adapters and coax cable will 
also see lots of heating with big mismatches. These can fail also; in fact we 
see that a lot. That’s why you see lots of admonitions to only use high quality 
connectors and adapters. Right angle adapters are especially bad as the 
conductor tends to migrate and short out at high power. Be sure that you use 
coax that is rated for the power levels as well. 

73,
Jack, W6FB


> On Jul 11, 2021, at 3:51 PM, Alan Bloom  wrote:
> 
> I can't speak directly about Elecraft tuners, but I did design an antenna 
> tuner when I was at Drake many years ago.
> 
> We specified the Drake MN-2700 at 5:1 SWR.  I made sure it would match that 
> SWR at all phase angles on all specified bands.
> 
> Typically the low-impedance end tends to be the hardest to match, at least on 
> the low bands.  So 50/5 = 10 ohms resistive is harder to match than 50*5 = 
> 250 ohms resistive even though the SWR is 5:1 in both cases.  That's because 
> the low impedances need larger tuning capacitors.  The Drake tuner would 
> typically match well above 5:1 into a high impedance but only barely meet 
> spec into a low impedance.  I suspect the Elecraft tuners are similar.
> 
> Alan N1AL
> 
> 
> On 7/11/2021 12:58 PM, Al Lorona wrote:
>> This question is about how manufacturers spec the matching range of their 
>> antenna tuners.
>> 
>> If an antenna system presents an impedance of 5 + j0 ohms to the antenna 
>> tuner, that's an SWR = 10 to 1.
>> 
>> But, an antenna impedance of 50 - j143 ohms is also SWR = 10. So is 110 - 
>> j200 ohms.
>> 
>> When a manufacturer like Elecraft says, "Our antenna tuner can match a 10:1 
>> mismatch," does that mean the tuner can match the first case above, the 
>> second case, the third case, or all three?
>> 
>> I guess what I'm asking is, are all of the impedances above equally 
>> difficult for the same tuner to match? Or is one 'harder' than the others? 
>> It would depend on the values of the L and C in the tuner, wouldn't it? 
>> Which implies that certain 10:1 mismatches are not tunable?
>> 
>> Thanks,
>> 
>> Al  W6LX/4
>> 
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Re: [Elecraft] Question about antenna matching

[Alan Bloom]

I can't speak directly about Elecraft tuners, but I did design an 
antenna tuner when I was at Drake many years ago.


We specified the Drake MN-2700 at 5:1 SWR.  I made sure it would match 
that SWR at all phase angles on all specified bands.


Typically the low-impedance end tends to be the hardest to match, at 
least on the low bands.  So 50/5 = 10 ohms resistive is harder to match 
than 50*5 = 250 ohms resistive even though the SWR is 5:1 in both 
cases.  That's because the low impedances need larger tuning 
capacitors.  The Drake tuner would typically match well above 5:1 into a 
high impedance but only barely meet spec into a low impedance.  I 
suspect the Elecraft tuners are similar.


Alan N1AL


On 7/11/2021 12:58 PM, Al Lorona wrote:

This question is about how manufacturers spec the matching range of their 
antenna tuners.

If an antenna system presents an impedance of 5 + j0 ohms to the antenna tuner, 
that's an SWR = 10 to 1.

But, an antenna impedance of 50 - j143 ohms is also SWR = 10. So is 110 - j200 
ohms.

When a manufacturer like Elecraft says, "Our antenna tuner can match a 10:1 
mismatch," does that mean the tuner can match the first case above, the second case, 
the third case, or all three?

I guess what I'm asking is, are all of the impedances above equally difficult 
for the same tuner to match? Or is one 'harder' than the others? It would 
depend on the values of the L and C in the tuner, wouldn't it? Which implies 
that certain 10:1 mismatches are not tunable?

Thanks,

Al  W6LX/4

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Re: [Elecraft] Question about antenna matching

[Dave]

I take it to mean, the tuner will "probably" match any halfway well 
designed antenna...


73, and thanks,
Dave (NK7Z)
https://www.nk7z.net
ARRL Volunteer Examiner
ARRL Technical Specialist, RFI
ARRL Asst. Director, NW Division, Technical Resources

On 7/11/21 11:58 AM, Al Lorona wrote:

This question is about how manufacturers spec the matching range of their 
antenna tuners.

If an antenna system presents an impedance of 5 + j0 ohms to the antenna tuner, 
that's an SWR = 10 to 1.

But, an antenna impedance of 50 - j143 ohms is also SWR = 10. So is 110 - j200 
ohms.

When a manufacturer like Elecraft says, "Our antenna tuner can match a 10:1 
mismatch," does that mean the tuner can match the first case above, the second case, 
the third case, or all three?

I guess what I'm asking is, are all of the impedances above equally difficult 
for the same tuner to match? Or is one 'harder' than the others? It would 
depend on the values of the L and C in the tuner, wouldn't it? Which implies 
that certain 10:1 mismatches are not tunable?

Thanks,

Al  W6LX/4

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[Elecraft] Question about antenna matching

[Al Lorona]

This question is about how manufacturers spec the matching range of their 
antenna tuners.

If an antenna system presents an impedance of 5 + j0 ohms to the antenna tuner, 
that's an SWR = 10 to 1.

But, an antenna impedance of 50 - j143 ohms is also SWR = 10. So is 110 - j200 
ohms.

When a manufacturer like Elecraft says, "Our antenna tuner can match a 10:1 
mismatch," does that mean the tuner can match the first case above, the second 
case, the third case, or all three?

I guess what I'm asking is, are all of the impedances above equally difficult 
for the same tuner to match? Or is one 'harder' than the others? It would 
depend on the values of the L and C in the tuner, wouldn't it? Which implies 
that certain 10:1 mismatches are not tunable?

Thanks,

Al  W6LX/4

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